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Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , kasan-dev , Linux Memory Management List , Linux-Arch , LKML Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A2868140003 X-Stat-Signature: 311xi4joqmwh3qufpc89epnewkkao8ag X-HE-Tag: 1673342121-96661 X-HE-Meta: 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 fWSvhfqV 2WcWEXy0OGTzv2vLJ7xfQIqaDNyDkIGZEU1P5HOqiKhtF8xds3nnVX1j+BQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: > > > Unfortunately, it can not be dynamically enabled because the size of > > > 'struct page' is unfortunately recorded in the metadata of the device. > > > Recall this is for supporting platform configurations where the capacity > > > of the persistent memory exceeds or consumes too much of System RAM. > > > Consider 4TB of PMEM consumes 64GB of space just for 'struct page'. So, > > > NVDIMM subsystem has a mode to store that page array in a reservation on > > > the PMEM device itself. > > > > Sorry, I might be missing something, but why cannot we have > > > > #ifdef CONFIG_KMSAN > > #define MAX_STRUCT_PAGE_SIZE 128 > > #else > > #define MAX_STRUCT_PAGE_SIZE 64 > > #endif > > > > Possibly because this needs to be a fixed size on permanent storage > (like an inode on a disk file system) > Ah, thank you, that makes sense. Then I'm assuming some contents of struct pages are also stored in the persistent memory. What happens if sizeof(struct page) stays below MAX_STRUCT_PAGE_SIZE, but the layout changes? E.g. doesn't it cause problems if the user enables/disables CONFIG_MEMCG?